This proposal will demonstrate proof of concept for a whole parasite (WP) vaccine directed against Plasmodium falciparum (Pf) sexual and mosquito stages (SMS) that will be used alone or in combination with PfSPZ Vaccine for interrupting malaria transmission (VIMT) from the human host to the mosquito vector. Such a PfSMS-WP-VIMT will be an ideal complement to the PfSPZ Vaccine, which has shown complete protection against parasite infection in recent clinical trials. If the PfSPZ Vaccine prevents infection and transmission in 90% of recipients and PfSMS-WP-VIMT prevents transmission in 90% of recipients, the combination will prevent transmission in at least 99% of recipients. The PfSMS-WP-VIMT offers major advantages to a subunit PfSMS vaccine based on one or a few antigens. This vaccine approach will increase the chance that more individuals will have protective immune responses and reduce the possibility of the parasites being able to select for evasion of immune responses by dramatically increasing the number of immunogens against which protective antibodies are induced. When used in combination with PfSPZ Vaccine, PfSMS-WP-VIMT will prevent transmission of parasites that may be selected for resistance to PfSPZ Vaccine. Sanaria uniquely produces Pf gametocytes (sexual stages) under GMP conditions and now consistently produces a mixture of gametes, zygotes and ookinetes, enriched for ookinetes, in vitro. We partially purified these parasites, immunized mice with the preparation in adjuvant, and showed that the sera from the immunized mice completely (100%) inhibited transmission of parasites to mosquitoes. We will exploit Sanaria's unique expertise in GMP-compliant gametocyte production and in vitro PfSPZ production, as well as extensive experience in parasite purification and in vivo transmission blocking feeding assays to develop, produce and test PfSMS-WP- VIMT. We will produce cultures of PfSMS from three time points (30-60 min, 8 h and 30 h) to ensure that all PfSMS stages are present. We will purify PfSMS in these cultures away from RBCs to obtain purified vaccine preparations. Proof of concept will be demonstrated by immunizing mice with the PfSMS-WP preparations in combination with adjuvants, then testing for antibody responses against cultured parasites and known PfSMS antigens, and for transmission blocking activity in an in vivo standard membrane feeding assay. The lead candidates will be further tested in mice for interactions with the PfSPZ Vaccine after co-administration by direct venous inoculation (DVI). In Phase II we will finalize methods for scaled-up manufacturing in compliance with cGMPs and quality control (QC) release and stability assays, manufacture in compliance with cGMPs, conduct QC release assays, initiate QC stability studies, conduct pre-clinical toxicology studies, design a clinical trial, and prepare al information for an Investigational New Drug application (IND).